I'm sure this is playable, because flexibility is valuable, but it is interesting how "bad" it is compared to its fixed mana friends:

At X=0 or 1, I doubt you would ever play this
At X=2, you'd rather play Catalog for U less;
At X=3 it is just a bad Jace's Ingenuity, or a worse-costed Enhanced Awareness;
At X=4, it nets you one less card than Opportunity or Dragonlord's Prerogative.

But all that said, I'd run it in a blue control deck if such a deck was viable. Or limited.

This looks amazing at X>5, and decent even below that. Sure, it doesn't have the incidental lifegain that Sphinx's Revelation had, but in exchange you get to dig one card deeper for the same cost. The discard is only a minor drawback, and plenty of decks can even spin it into an advantage. Overall this seems like an automatic inclusion in pretty much any Standard control deck.